<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
    <script src="vue.js"></script>
</head>
<body>
<div id="app">
    {{fullName}}
    {{age}}
</div>
<script>
    var vm = new Vue({
        el: "#app",
        data: {
            firstName: "Dell",
            lastName: "Lee",
            fullName: "Dell Lee",
            age: 28
        },
        watch: {
            firstName: function () {
                console.log("计算了一次")
                this.fullName = this.firstName + this.lastName;
            },
            lastName: function () {
                console.log("计算了一次")
                this.fullName = this.firstName + this.lastName;
            }

        }
        //方法
        // methods: {
        //     fullName: function () {
        //         return this.firstName + " " + this.lastName
        //     }
        // }
        //计算属性
        // computed: {
        //     fullName: function () {
        //         console.log("计算了一次")
        //        return this.firstName + " " + this.lastName
        //     }
        // }

    })

</script>

</body>
</html>